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36887ed392
1. The previous color contrast calculation function was incorrect at least for the `#84b6eb` where it output low-contrast white instead of black. I've rewritten these functions now to accept hex colors and to match GitHub's calculation and to output pure white/black for maximum contrast. Before and after: <img width="94" alt="Screenshot 2024-04-02 at 01 53 46" src="https://github.com/go-gitea/gitea/assets/115237/00b39e15-a377-4458-95cf-ceec74b78228"><img width="90" alt="Screenshot 2024-04-02 at 01 51 30" src="https://github.com/go-gitea/gitea/assets/115237/1677067a-8d8f-47eb-82c0-76330deeb775"> 2. Fix project-related issues: - Expose the new `ContrastColor` function as template helper and use it for project cards, replacing the previous JS solution which eliminates a flash of wrong color on page load. - Fix a bug where if editing a project title, the counter would get lost. - Move `rgbToHex` function to color utils. @HesterG fyi --------- Co-authored-by: delvh <dev.lh@web.de> Co-authored-by: Giteabot <teabot@gitea.io>
58 lines
1.9 KiB
Go
58 lines
1.9 KiB
Go
// Copyright 2023 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package util
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import (
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"fmt"
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"strconv"
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"strings"
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)
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// Get color as RGB values in 0..255 range from the hex color string (with or without #)
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func HexToRBGColor(colorString string) (float64, float64, float64) {
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hexString := colorString
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if strings.HasPrefix(colorString, "#") {
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hexString = colorString[1:]
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}
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// only support transfer of rgb, rgba, rrggbb and rrggbbaa
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// if not in these formats, use default values 0, 0, 0
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if len(hexString) != 3 && len(hexString) != 4 && len(hexString) != 6 && len(hexString) != 8 {
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return 0, 0, 0
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}
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if len(hexString) == 3 || len(hexString) == 4 {
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hexString = fmt.Sprintf("%c%c%c%c%c%c", hexString[0], hexString[0], hexString[1], hexString[1], hexString[2], hexString[2])
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}
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if len(hexString) == 8 {
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hexString = hexString[0:6]
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}
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color, err := strconv.ParseUint(hexString, 16, 64)
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if err != nil {
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return 0, 0, 0
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}
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r := float64(uint8(0xFF & (uint32(color) >> 16)))
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g := float64(uint8(0xFF & (uint32(color) >> 8)))
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b := float64(uint8(0xFF & uint32(color)))
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return r, g, b
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}
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// Returns relative luminance for a SRGB color - https://en.wikipedia.org/wiki/Relative_luminance
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// Keep this in sync with web_src/js/utils/color.js
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func GetRelativeLuminance(color string) float64 {
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r, g, b := HexToRBGColor(color)
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return (0.2126729*r + 0.7151522*g + 0.0721750*b) / 255
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}
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func UseLightText(backgroundColor string) bool {
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return GetRelativeLuminance(backgroundColor) < 0.453
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}
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// Given a background color, returns a black or white foreground color that the highest
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// contrast ratio. In the future, the APCA contrast function, or CSS `contrast-color` will be better.
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// https://github.com/color-js/color.js/blob/eb7b53f7a13bb716ec8b28c7a56f052cd599acd9/src/contrast/APCA.js#L42
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func ContrastColor(backgroundColor string) string {
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if UseLightText(backgroundColor) {
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return "#fff"
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}
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return "#000"
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}
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